The present invention relates to a dry powder feed and charging devices that can, for example, be used in dry powder deposition apparatuses.
The applicants have previously described apparatuses and techniques for using electromagnetic forces to make controlled depositions of materials. Such depositions make it possible to deposit controlled amounts of, for example, a pharmaceutical onto spatially resolved areas of a substrate. Described herein are further improvements to the methods and techniques for controlled deposition. In particular, the invention provides cyclones, powder feeds and deposition stations that can improve powder charging, powder consistency, powder sizing, reproducibility of deposition, and other aspects of handling powders.
The present invention provides improvements in handling fluidized powder dispersed in a carrier gas. Within a device of the invention, powders of particle aggregates and particle grains can be reduced in size via collisions with particulate matter carried by a gas or by collisions with a surface of the device. Particles can be charged by, for example, triboelectric, inductive or corona charging methods within the inventive system. The invention further provides for improved efficiency in the dispersion and charging of powders in a carrier gas by, for example, amplifying the internal flow rate of the gas/powder mixture while further providing a controllable, typically slower, rate of powder output. The powder output can be made up of particles of a selected charge polarity. Another aspect of the invention relates to the optical monitoring of the amount of fluidized powder flux.
The invention provides, together with associated methods, a powder feed comprising: a venturi comprising an external gas inlet, a gas outlet through which gas flows at a rate amplified over a gas flow rate into the external gas inlet, and an internal gas inlet; and a cyclone with an intake port connected to the venturi gas outlet, a recycle outlet port, and a product port, wherein a gas flow rate FS into the venturi external gas inlet results in an enhanced flow rate into the cyclone intake port.
The invention further provides, together with associated methods, a cyclone comprising: a milling chamber adapted to cause, under the force provided by a flow of gas, particles therein to collide with the chamber or other particles to mill the particles; a product output port located on the milling chambe/r to preferentially favor the output of milled particles, wherein the product output port is electronically isolated from the milling chamber; an electrical power source; and an electrical conduit that can be opened or closed for conveying from the power source a potential to the product output port.
The invention also provides, together with associated methods, a powder feed cell comprising: a chamber with an outlet port; a gas input conduit; and a venturi located within the chamber and connected to the gas input conduit, wherein the venturi has inlet port that draws fluidized powder from within the chamber and an outlet port that expels fluidized powder within the chamber, and wherein when gas flows into the venturi from the gas input conduit the venturi effect draws gas through the inlet port and proportionately increases gas flow at the outlet port, wherein the gas flow from the venturi outlet port is adapted to suspend at least a portion of a powder located within the chamber.
The invention also provides, together with associated methods, a powder handling device comprising: a cyclone comprising one or more surfaces along which fluidized powder flows during operation of the cyclone; and a source conduit of fluidized powder connected to the cyclone comprising a venturi effective to create turbulence in the fluidized powder.
The invention also provides, together with associated methods, a powder coating device comprising: a conduit for conveying charged powder particles suspended in a gas flow; and a depression, wherein powder particles suspended in the gas flow deposit on the internal surface of the depression.
The invention further provides, together with associated methods, a powder flux detecting device comprising: a conduit for carrying gas-fluidized powder, the conduit with an upstream end and a downstream end towards which the fluidized powder flows, in which conduit is incorporated a venturi is adapted to increase gas flow or turbulence in the gas flow; at least one laser directing a laser beam across the conduit, the laser comprising a window separating it from the conduit; and at least one detector adapted to intercept the laser beam or light scattered from the laser beam, the detector comprising a second window separating it from the conduit, wherein the laser and detector are positioned downstream of the venturi and in sufficient proximity so that increased gas flow or increased turbulence reduces powder coating of the first and second windows from that which would occur in the absence of a proximate venturi.